Turkey's military said it invited Russian military attaches to its headquarters and explained that Ankara shot down the Russian jet because its rules of engagement went into effect after the plane did not respond to the alleged warnings.

In a written statement on Wednesday, Turkish armed forces said they had made great efforts to find and rescue the pilots of the plane, and had called military authorities in Moscow to express readiness for "all kinds of cooperation".

"The nationality of the plane was not known ... and the rules of engagement were automatically used" after the plane did not respond to "10 different warnings", the military said.

"All questions have been answered, radar maps have been used to explain the issue to the Russian side and [our] readiness to share any kind of information have been expressed."

Meanwhile, fighting has resumed in Kassab, Syria, where the Russian jet came down, further complicating investigations into the incident.